Collins' appearance outside the yard's Gate 1 occurred on the last day of a three-day, 350-mile leg of her campaign bus tour of Maine. She is running for re-election to her Senate fourth term.

Mark Nelson of the International Federation of Professional and Technical Engineers, which represents about 1,500 shipyard workers, emphasized what he sees as Collins' tenure and independence as key to his union's endorsement.

"Any time there is a big issue or problem in Washington, while a lot of senators are running out to get their faces on entertainment news channels, there's a small group of senators who go off to try to work on a compromise," he said. "No matter how many are on that list — eight, seven, six or even two — I know one name that will always be on it, and that is Susan Collins."

Nelson said he was also appreciative that Collins worked across the aisle and with House members to ensure public shipyard workers were not furloughed during the government shutdown last fall.

Collins was also endorsed by the International Union of Painters and Allied Trades/New England Council and the Laborers' International Union of North America/New England Council.